1. Field of the Invention
The present invention relates to an apparatus of detecting an obstacle of a vehicle such as an unmanned vehicle.
2. Description of the Related Art
An unmanned vehicle such as an unmanned dump truck operated in a wide site such as a quarrying site or a mine, automatically detects an obstacle in front of the vehicle and is automatically controlled to run based on a result of the detection. In this case, an unmanned vehicle such as an unmanned dump truck is generally wide in the vehicle width, a width of a running road therefor is also wide and therefore, in an obstacle detecting apparatus mounted on the unmanned vehicle, there is requested a function capable of catching an obstacle in a wide detection area.
As an obstacle detecting apparatus, there have conventionally known various kinds of radars such as an optical laser, a millimeter wave radar, and a visual sensor.
The radar is provided with an advantage of high accuracy and is preferable for mounting on an unmanned vehicle. In mounting the radar on the unmanned vehicle, there are various systems for covering the wide detection area as shown by items 1), 2), and 3), described below.
1) Fixed Scanning Radar System:
According to the system, as shown by FIG. 11(a), a radar 2 is mounted on an unmanned vehicle 1 and radar beam 3 is scanned at high speed in a left and right direction in a range of about xc2x110xc2x0 to thereby detect an obstacle 60 on a running road 50.
2) Rotary Radar System:
According to the system, as shown by FIG. 11(b), the radar 2 is mounted on the unmanned vehicle 1 and the radar beam 3 is rotated by 360xc2x0 centering on the unmanned vehicle 1 to thereby detect the obstacle 60 on the running road 50.
3) Pivoting Scanning Radar System:
According to the system, as shown by FIG. 11(c), the radar 2 is mounted on the unmanned vehicle 1 via a pivoting base, the radar beam 3 is scanned at high speed in the left and right direction in a range of about xc2x110xc2x0 and the radar beam 3 is pivoted by pivoting the pivoting base at low speed to thereby detect the obstacle 60 on the running road 50.
An absolute position of the obstacle 60 can be measured by measuring an azimuth angle (scanning angle) of the radar beam 3 and a distance from the radar 2 to the obstacle 60 and based on measured values of these and the position and the azimuth angle of the unmanned vehicle 1. Further, in the case of the pivoting scanning radar system of the above-described item 3), it is necessary to measure the absolute position of the obstacle 60 by measuring a pivoting angle of the pivoting base.
Further, there is also known a technology combined with the above-described items 1) and 3). For example, according to JP-A-4-163250, there is described invention with regard to a rear view sensor of a general automobile combining the fixed radar system of item 1) and the pivoting radar system of item 3) and the pivoting radar is pivoted in a direction of the obstacle caught by the fixed radar to thereby further catch the obstacle by the pivoting radar.
Further, in U.S. Pat. No. 5,612,883, there is described invention changing a scanning range in a pivoting scanning radar system.
Further, according to the literature, there is described invention successively measuring absolute positions of respective objects detected by radar beam to thereby determine whether the respective objects are the same obstacle.
When the fixed scanning radar system of FIG. 11(a) is adopted, although accuracy in measuring the azimuth angle of the radar beam 3 is excellent and the obstacle 60 on a running road having a small curve can be detected, since a scanning area of the radar beam 3 is narrow, dead angle is present at a cross point and a sharp curve and there is a concern of overlooking the obstacle 60.
Further, when the rotary radar system of FIG. 11(b) is adopted, the radar beam 3 is rotated by 360xc2x0 and therefore, there is not dead angle, however, since a detection period is long, it is wasteful to only detect the obstacle 60 on the front side and a considerable period of time is required for catching the obstacle 60. Particularly, when the unmanned vehicle 1 is running at high speed (50 km/h), a considerable distance may be run until detecting the front obstacle 60 and there is a concern of interfering with the obstacle 60.
When the pivoting scanning radar system of FIG. 11(c) is adopted, there is not the dead angle and also the detection period is short and therefore, the system covers drawbacks of the fixed scanning radar system and the rotary radar system.
However, in order to measure the absolute position of the obstacle 60, not only the azimuth angle (scanning angle) of the radar beam 3 and the azimuth angle of the unmanned vehicle but also a pivoting angle of the pivoting base must be measured and measurement errors of the angles are accumulated to thereby enlarge measurement error of the position of the obstacle. Since accuracy of the angles are poor in this way, the obstacle 60 at outside of the running road 50 is liable to be detected erroneously as the obstacle 60 in the running road 50.
The invention has been carried out in view of the actual situation and it is a problem to be resolved to eliminate the dead angle, to be able to shorten the detection period and to reduce erroneous detection of the obstacle in detecting the obstacle of the vehicle.
Now, as described above, according to U.S. Pat. No. 5,612,833, in order to determine the same obstacle, the absolute positions of the respective objects are successively measured.
However, when the absolute positions of the objects are successively measured, the operational processing becomes complicated.
Hence, according to the invention, it is a problem to be resolved to be able to determine the same obstacle without carrying out the complicated operational processing.
According to a first aspect of the invention, there is provided an obstacle detecting apparatus of a vehicle for detecting an obstacle of a vehicle by using a radar, the obstacle detecting apparatus comprising a fixed radar fixed to the vehicle, and a pivoting radar pivotable relative to the vehicle, wherein the pivoting radar is pivoted in a direction in accordance with a progressing direction of the vehicle such that radar beam is emitted in the direction in accordance with the progressing direction of the vehicle.
According to the first aspect of the invention, as shown by FIG. 6, when a vehicle 1 runs on a running road 50, by pivoting a pivoting radar 24 in a direction in accordance with a progressing direction of the vehicle 1, a total or a portion of a detection range 3B of the pivoting radar 24 can be made to be outside of a detection range 3A of fixed radars 21 through 23. Therefore, an obstacle 60 in a range outside of the detection range of the fixed radars 21 through 23 can be detected by the pivoting radar 24.
Therefore, in detecting the obstacle 60 of the vehicle 1, dead angle can be eliminated. That is, since the fixed radars 21 through 23 and the pivoting radar 24 are provided, the detection range of the obstacle can be covered with respect to both a linear road or the running road 50 having a large radius of curvature shown in FIG. 7 and the running road 50 having a small radius of curvature such as a cross point or a sharp curve shown in FIG. 6. Further, since both of the fixed radars 21 through 23 and the pivoting radar 24 are used, a detection period can be shortened. Further, since the pivoting radar 24 is used along with the fixed radars 21 through 23, erroneous detection of the obstacle can be reduced.
According to a second aspect of the invention, there is provided an obstacle detecting apparatus of a vehicle for detecting an obstacle of a vehicle by using a radar, the obstacle detecting apparatus comprising a fixed radar fixed to the vehicle, and a pivoting radar pivotable relative to the vehicle, wherein by simultaneously emitting fluxes of radar beam from both of the fixed radar and the pivoting radar, the same obstacle is detected by the two radars.
According to the second aspect of the invention, as shown by FIG. 7, when the vehicle 1 runs on the running road 50, both of the fixed radars 21 through 23 and the pivoting radar 24 are simultaneously and redundantly detect the obstacle 60 and therefore, the obstacle 60 can be detected highly reliably.
According to a third aspect of the invention, there is provided an obstacle detecting apparatus of a vehicle for detecting an obstacle of a vehicle by using a radar, the obstacle detecting apparatus comprising a fixed radar fixed to the vehicle, and a pivoting radar pivotable relative to the vehicle, wherein the pivoting radar is pivoted such that radar beam is emitted in a range outside of a detection range of radar beam emitted from the fixed radar.
According to the third aspect of the invention, as shown by FIG. 6, when the vehicle 1 runs on the running road 50 having a small radius curvature, by pivoting the pivoting radar 24, a total or a portion of the detection range 3B of the pivoting radar 24 can be made to be outside of the detection range 3A of the fixed radars 21 through 23 and by the pivoting radar 24, the obstacle 60 in the range outside of the detection range of the fixed radars 21 through 23 can be detected by the pivoting radar 24.
According to a fourth aspect of the invention, in the first or second or third aspect of the invention, different weights are added to a case of detecting an object by the fixed radar and a case of detecting the object by the pivoting radar and the detected object is determined to be the obstacle based on a total value of the weights.
The fixed radars 21 through 23 are not pivoted and therefore provided with small error in angle accuracy, excellent in accuracy of measuring the position of the obstacle 60, hardly detect erroneously that the obstacle 60 is outside of the running road 50 and is highly reliable.
In contrast thereto, the pivoting radar 24 is pivoted and therefore is provided with a large error in the angle accuracy, poor in the accuracy of measuring the position of the obstacle 60, frequently detects erroneously that the obstacle 60 is outside of the running road 50 and is provided with low reliability.
In this way, the reliability differs for the respective xe2x80x9cradar systemsxe2x80x9d and therefore, weight (count) is made to differ according to the respective systems. That is, as shown by FIG. 8, the fixed radars 21 through 23 are more reliable than the pivoting radar 24 and therefore, is given a weight (count) larger than a weight (count) when the obstacle is detected by the pivoting radar 24.
In this way, there is added weight (count) which differs by the case of detecting the object by the fixed radars 21 through 23 and the case of detecting the object by the pivoting radar 24 and the detected object is determined to be the xe2x80x9cobstaclexe2x80x9d based on a total value of the weights (counts).
According to a fifth aspect of the invention, there is provided an obstacle detecting apparatus of a vehicle for detecting an obstacle of a vehicle by using a radar, the obstacle detecting apparatus comprising a fixed radar fixed to the vehicle and a pivoting radar pivotable relative to the vehicle, wherein different weights are added to a case of detecting an object by the fixed radar and a case of detecting the object by the pivoting radar and the detected object is determined to be the obstacle based on a total value of the weights.
The fifth aspect of the invention is the aspect of invention constituting an independent aspect by the fourth aspect of the invention.
According to a sixth aspect of the invention, there is provided an obstacle detecting apparatus of a vehicle for detecting an obstacle of a vehicle by using a radar wherein the vehicle is mounted with a plurality of radars which differ in at least either one of a system and a kind thereof, different weights are added for the respective systems and the respective kinds of the radars, and when an object is detected by the respective radars, the detected object is determined to be the obstacle based on a total value of the weights.
The fifth aspect of the invention is applicable to a case of combining three or any two of the respective radar systems shown in FIGS. 11(a), 11(b) and 11(c). For example, the fixed radar system of FIG. 11(a) and the rotary radar system of FIG. 11(b) are combined, there is added the weight (count) which differs by the case of detecting the object by the fixed radar and the case of detecting the object by the rotary radar and the detected object is determined to be the xe2x80x9cobstaclexe2x80x9d based on a total value of the weights (counts).
Further, the weight (count) can be made to differ also in accordance with the kind of radar (whether the radar is an optical radar, or a millimeter wave radar, or a visual sensor).
According to a seventh aspect of the invention, there is provided an obstacle detecting apparatus of a vehicle for detecting a plurality of obstacles of a vehicle by using a radar, the obstacle detecting apparatus comprising predicted distance calculating means for successively calculating, when an object is detected by the radar, a predicted distance from the vehicle to the detected object thereafter, distance measuring means for measuring a distance from the vehicle to the detected object at each time of detecting the object by the radar, count adding means for comparing a distance measured by the distance measuring means and the predicted distance calculated by the predicted distance calculating means, determining whether the detected object is the same as the object detected in the past and successively adding a count of a corresponding one of the detected object when the detected object is determined to be the same as the object detected in the past at each time of detecting the object by the radar, and obstacle determining means for determining that the corresponding one of the detected object is the obstacle when the counts added by the count adding means become equal to or larger than a predetermined threshold.
As shown in FIG. 9(b), at each time of detecting an obstacle candidate 61 (62, 63) by radars 21 through 24, as described above, a distance R from the vehicle 1 to the obstacle candidate 61 (62, 63) is measured.
Meanwhile, at an inner portion of the vehicle 1, as shown by FIG. 9(a), when the obstacle candidate 61 (62, 63) is newly detected by the radars 21 through 24, thereafter, a predicted distance Rexp from the vehicle 1 to the obstacle candidate 61 (62, 63) is successively calculated at each time of elapse of a predetermined time period xcex94t.
Further, at each time of detecting the obstacle candidate 61 (62, 63) by the radars 21 through 24, the measured distance R and the predicted distance Rexp are compared and it is determined whether the detected obstacle candidate is the same as the obstacle candidate detected in the past.
As a result, when it is determined that the detected obstacle candidate is the same as the obstacle candidate detected in the past, a constant count is successively added to a kind of a list of the obstacle candidate.
Further, when the count of the list becomes equal to or larger than a predetermined threshold (100 points), the obstacle candidate of the list is determined to be the xe2x80x9cobstaclexe2x80x9d.
According to the seventh aspect of the invention, it is not necessary to successively measure an absolute position of respective objects in order to determine the same obstacle as in U.S. Pat. No. 5,612,883, described above, but the distance may be measured and predicted. Therefore, in comparison with the case of successively measuring the absolute position of the object, the calculating processing is simplified and the same obstacle can be determined without carrying out complicated calculating processing.